I didnt say the album will sound better, I said the label is more willing to give them more money. Most good bands make a good product. In the situation of a metallica, i dont know what went wrong there but,
If you ask metallica, I am sure they think their albums sounds superb.
Some will complain about a COB production as well. It is all subjective. The point is a label will give more money to a band that sells, hence there is more to pay back. and again A BAND CANNOT EARN UNTIL THEY PAY WHAT IS OWED. No one ever seems to address that.

When a Band signes to a label they usually give the rights away of their music for a set period of time and at some point it will come back to the band. You are wrong when you say a band gets 50% royalty off the download. Especially if they are signed to a label. Have you signed a digital license deal through a label? I sure have and it did not work like that for either group from either label I was on. I sure know a ton of bands that would love to get that magic 50% you speak of.